The long acting synthetic narcotic methadone is a potent inhibitor of the in vivo and in vitro growth of human lung cancer cells and the inhibition appears to be mediated by specific, non-conventional, high affinity methadone binding sites, distinct from the sites present in human brain and normal lung. Based on these results, a clinical trial of methadone therapy for lung cancer patients has been initiated. The goal of the proposed research is (1) to purify, characterize and clone the corresponding genes for methadone receptors present on human lung cancer cells, human brain and normal lung, in order to determine the existence of multiple methadone receptor types in normal and tumor tissues and/or the central (CNS) and peripheral nervous systems (PNS); and (2) to elucidate the molecular mechanisms involved in the growth inhibiting actions of methadone in human lung cancer cells. Purification of the receptors will be carried out using affinity chromatography, and biochemical and pharmacological characteristics of the purified receptors will be determined. Cloning of the methadone receptor expressed in lung cancer cells will be carried out using amino acid sequences of the purified receptor and PCR techniques. The mechanism of action of methadone in human lung cancer cells will be determined by studying (a) its role in the regulation of apoptosis; (b) the signal transduction pathways involved in its apoptotic effect, such as the regulation of protein kinase C activity; and (c) changes in gene expression leading to growth inhibition. These studies should lead to a better understanding of the PNS and CNS effects of this drug and the design of better treatment protocols for its use in the control of cancer growth and pain, as well as in drug abuse programs.